FIGS. 1 and 2 depict a prior art hydronic boiler 10 having a heat exchanger 12 incorporating upper and lower headers 14, 16. Upper header 14's finned heat exchange tubes 18 are fluidicly coupled between front and rear pipe portions of upper header 14. Lower header 16's finned heat exchange tubes 19 are fluidicly coupled between front and rear pipe portions of lower header 16. Riser pipes 20 fluidicly couple the rear pipe portions of upper and lower headers 14, 16 respectively.
Water to be heated is pumped into heat exchanger 12 via inlet pipe 22 which is fluidicly coupled to inlet port 23 provided in the front pipe portion of lower header 16. The water flows from inlet port 23 into the front pipe portion of lower header 16, then flows through one of finned tubes 19 to the rear pipe portion of lower header 16, then flows through one of riser pipes 20 to the rear pipe portion of upper header 14, then flows through one of finned tubes 18 to the front pipe portion of upper header 14, and ultimately exits heat exchanger 12 by flowing through an outlet port (not shown) provided in the front pipe portion of upper header 14.
Heat is provided by burner tubes 24 which burn natural gas or propane gas supplied to burner tubes 24 through gas manifold 26. Combustion air is drawn upwardly through apertured base pan 28 which is mounted beneath burner tubes 24. Hot gases emitted by burner tubes 24 flows between the heat exchange fins which spirally and circumferentially surround tubes 18, 19 thus heating the fins, tubes 18, 19 and the water flowing therethrough. Refractory insulation material 30 surrounds heat exchanger 12 and burner tubes 24. After flowing between the heat exchange fins of tubes 18, 19 as aforesaid, the hot gases are exhausted through flue collector nozzle 32.
Prior art baffles 34 are provided between the upper, longitudinally extending portions of each adjacent pair of finned tubes 18 or 19, and between each outermost finned tube 18 or 19 and the adjacent refractory insulation 30. Baffles 34 are typically metal bars having a “T” cross-sectional shape, a flattened “V” cross-sectional shape, or an arcuate “V” cross-sectional shape conforming to the outer curvature of finned tubes 18, 19. As depicted in FIGS. 1 and 2, baffles 34 have a “T” cross-sectional shape. Baffles 34 deflect hot gases emitted by burner tubes 24 toward finned tubes 18, 19 to improve heat transfer through finned tubes 18, 19 to water flowing therethrough. Without baffles 34, heat transfer efficiency is reduced, since a considerable portion of the hot gases emitted by burner tubes 24 escapes through finned tubes 18, 19 into flue collector nozzle 32 without contributing significantly to heating of finned tubes 18, 19 or water flowing therethrough.
This invention provides an improved baffle for enhancing the heat transfer efficiency of a gas-fired hydronic boiler heat exchanger.